In recent years, development of various types of information processing systems have accompanied rapid advance of the information industry, and recording methods and apparatuses appropriate for the information processing systems have also been developed and put into practical use.
Practically-used recording methods are, in addition to silver salt photography, the electrophotographic method, the inkjet recording method, the thermal recording method, the sublimation transfer method, the thermal transfer method, and the like. In any of the methods, sharp high-quality images with vivid hue should be formed.
Among these recording methods, for example, the inkjet recording method has widely been used not only in offices but also at home because 1) the inkjet recording method can perform recording on various types of recording materials, and 2) recording by the inkjet recording method can be conducted by compact and relatively-inexpensive hardware (apparatuses) with less noise.
Further, various types of inkjet recording media have been developed along with the recent improvement of the resolution of the image obtained by using inkjet printers and along with the recent development of hardware (apparatuses) for inkjet recording in recent years; as a result, it has become possible to obtain a so-called photograph-like recorded matter having high image quality.
Characteristics required particularly for an inkjet recording medium are generally as follows: (1) quick drying property (high ink absorbing rate) of the medium; (2) an adequate and uniform diameter of ink dots (without bleeding); (3) favorable graininess; (4) high roundness of dots; (5) high color density; (6) high color saturation (without dullness); (7) superior light resistance, gas resistance, and water resistance of printed portions; (8) high whiteness of the recording face; (9) superior storage stability of the recording medium (without yellowing or bleeding in a long-term storage); (10) superior dimensional stability and resistance to deformation (that suppresses curling to a sufficiently small degree); (11) superior running property on hardware; and the like. Further, glossy photographic paper which is used for the purpose of obtaining a photograph-like high-quality recorded matter is required to have the above-described characteristics and, in addition, glossiness, surface smoothness, and photographic-paper-like appearance similar to silver salt photographs.
A resin-coated paper has conventionally been used as a support which constitutes an inkjet recording medium in order to achieve glossiness, smoothness, and high image quality. The resin-coated paper has a paper base both sides of which are laminated with a polyethylene resin. However, the resin-coated paper does not absorb the ink solvent in the applied ink; therefore, when the paper is put in a file immediately after printing and stored, a problem is created in that bleeding of the image occurs over the time owing to the remaining ink solvent that has not evaporated.
In order to prevent the image bleeding, a support having no resin coating may be used to make an inkjet recording medium. When an ink-receiving layer is provided directly on an absorptive support such as a commercially-available paper base, the bleeding over time is reduced by the absorption of the ink solvent; however, a problem is created, for example in that the surface glossiness is markedly deteriorated.
In Japanese Patent Application Laid-Open (JP-A) No. 2001-301098, a support for image recording is disclosed. The support has paper whose both sides are coated with a resin capable of forming a film. The degree of glossiness defined by JIS P8142 of the paper surface on the side to be provided with the image is 20% or more, and the center surface average roughness SRa of the surface on the side to be provided with the image is 0.75 μm or less when measured under the condition of a cutoff of 6 to 7 mm. Although the support is excellent in smoothness, there is room for improvement of the image clarity
In addition, an inkjet recording sheet (member) having an ink-receiving layer is disclosed (refer to JP-A Nos. 9-174998 and 9-183268). The ink-receiving layer is composed of at least two layers. The lower layer is prepared by curing a layer containing a water-soluble electron-beam-curable resin, and the upper layer contains an adhesive and pigment particles having an average particle diameter of 1 μm or less. However, the surface roughness of this inkjet recording sheet (member) has not been examined, and it is not clear whether the glossiness of the inkjet recording sheet is good or bad.
Further, in JP-A No. 2001-63204, an inkjet recording medium having at least one ink-receiving layer containing a vapor-phase-method silica provided on a polyolefin-resin-coated paper support is disclosed. The support has a 75-degree specular glossiness of 30 to 70% and a center surface average roughness SRa of 0.11 to 0.50 (at wavelength: 0.8 mm). In this inkjet recording medium, problems of the ink absorbing property, glossiness and cracks have been solved to some extent, but has not been completely solved.